Robert F. "Toby" Fox (born October 11, 1991) is an American video game developer and composer. He is best known for developing the role-playing video games Undertale and Deltarune.
Fox's early work consisted of developing RPG Maker games and creating ROM hacks, including the EarthBound Halloween Hack. Fox then moved on to composing music, including for Andrew Hussie's 2009 webcomic Homestuck. In 2015, Fox created Undertale, which became a breakout hit and pop-culture phenomenon. It has received nominations for a British Academy Game Award, three Game Awards, and three D.I.C.E. Awards.
Following the success of Undertale, Fox went on to compose music for several other indie games, as well as contributing to the soundtracks of Super Smash Bros. Ultimate and the Pokémon video games. From 2018 onwards, Fox began releasing Chapters of Deltarune, an episodic video game set in a parallel universe to Undertale; the game has received critical acclaim.
Robert F. Fox was born on October 11, 1991, in Manchester, New Hampshire, the third of four brothers. Fox discovered the role-playing video game EarthBound when he was four years old after it was gifted to one of his older brothers for "Christmas or his birthday", and credited the game with helping him learn how to read. During church service around age five, he often drew fictional stage layouts based on the Mega Man X series. While Fox attended elementary school, his brothers told him about RPG Maker 2000—a program used to develop RPGs—and they began creating games together using it, including Toby's Adventure, Fox's first game. Fox learned about the Touhou Project franchise through a free games website at age 10, and played the demo versions of Embodiment of Scarlet Devil and Perfect Cherry Blossom.
Fox's interest in EarthBound was furthered at age 11 after discovering a fansite for the game, Starmen.net, which motivated him to create games to impress the site's members. Using the ROM hack editor PK Hack, which he considered his "entrance into [the] community", Fox created his first hack in middle school. Under the username Radiation, he released EarthBound Halloween Hack in 2008 as part of a ROM hacking competition on Starmen.net, additionally composing the song "Megalovania" for the hack's soundtrack. When Fox was disallowed by his parents from attending a yearly Starmen.net forum meetup due to his age, the forum's founder Reid Young advised Fox to threaten to "smoke a cigarette" if he wasn't allowed to attend, which ultimately worked. Fox additionally discovered the English fan translation of the RPG OFF through the forum.
Primarily a self-taught musician, Fox began relearning the piano during middle school to play video game music he knew by ear, having previously taken lessons in second grade; he also played the trumpet through high school. Fox recalled to Touhou Project creator ZUN that he had received a standing ovation following a piano rendition of "Necrofantasia" from Perfect Cherry Blossom during a high school summer camp gathering. As a senior, he began creating piano covers of music from the webcomic Homestuck, gaining recognition from its creator Andrew Hussie, and later became the music team's production coordinator. Fox is a graduate of Northeastern University.
After completing a downloadable demo by June 2013, Fox created a Kickstarter campaign for Undertale that month with a goal of $5,000, slating the game for a Summer 2014 release. The campaign ultimately raised over ten times that amount, totaling $51,124 from 2,398 people. Though Fox was initially "unsure if it was humanly possible to create [Undertale] before making the demo," he considerably expanded the game's scope following the demo's release. Fox used the Kickstarter's proceeds to continue working on the game until its release in September 2015. Undertale was developed almost entirely by Fox himself, except for some art assets.
Undertale released on September 15, 2015, to widespread critical acclaim, and has been ranked by numerous publications as one of the best video games of all time. Undertale's soundtrack has additionally been named one of the best video game soundtracks. Undertale gained immediate popularity on Steam, selling over 500 thousand copies within three months, doubling again to a million two months later. In GameFAQs's "Best. Game. Ever." poll that December, Undertale won against The Legend of Zelda: Ocarina of Time, the incumbent game from a similar 2009 poll, in a final vote of 156,000 participants. The game was nominated for various other accolades at game award ceremonies through the following year, including at the D.I.C.E. Awards, the Game Awards, and the Game Developers Choice Awards.
The rapid rise of the Undertale fandom's popularity and its behavior towards those who disliked the game led Fox to comment about the matter on Twitter in January 2016, where he stated, "It's OK if people don't like the game. I don't care," further hoping the game would have an "overall good effect on the world". In May 2016, internet personality MatPat gifted Pope Francis a Steam key of Undertale during a meeting between the Pope and numerous other YouTubers. Before Undertale's first anniversary, Fox made a retrospective post on Tumblr describing his feelings about the game's success and the stress the attention brought him, further referring to Undertale as "about an 8/10, niche RPG game." In November 2017, Fox was included on Forbes's 2018 list of 30 Under 30 in Games for his work on Undertale.
Fox initially conceived of the idea for his game Deltarune in a fever dream in 2011, with an initial version being created in 2012 before being abandoned. On October 30, 2018, Fox posted a request for fans of Undertale to check its official Twitter account in 24 hours. The following day, Fox released the first chapter of Deltarune for free under the guise of a "survey". Deltarune takes place in a parallel universe to the setting of Undertale, with Fox describing it as being "more enjoyable" to those that had completed it. At the time, Fox stated that he did not wish to spend longer than seven years on the project; he expressed interest in assembling a team to aid development, stating that without one he had "absolutely no estimation of its completion".
After Deltarune had been playable for several months, Fox stated he had hope he would complete its remainder, saying: "Slowly I'm writing and drawing it all out." He stated that he had already written about 50 songs past Chapter 1. On September 17, 2021, Fox released the second chapter of Deltarune for free since "the world has been really tough for everybody recently", referring to the struggles of the COVID-19 pandemic. He released the next two chapters, 3 and 4, bundled in with the first two as a paid game on June 4, 2025; future chapters will be added to it as free updates for owners of the paid version. On June 24, 2026, Chapter 5 was released, and Chapter 6 is projected to release in 2027. Deltarune is set to have a total of seven chapters.
Outside of Undertale and Deltarune, Fox has worked on other projects. The video game magazine A Profound Waste of Time has featured Fox as a contributor. The success of Undertale, especially in Japan, afforded Fox the opportunity to meet Super Smash Bros. creator Masahiro Sakurai. In September 2019, Sans, a character from Undertale, was later included in Super Smash Bros. Ultimate as a Mii costume available through downloadable content, along with an instrumental composition "Megalovania", for which Fox provided a new arrangement.